Seeing that he had scared Jiang Wangzhi half to death, Fang Xi decided not to push the man any further.
He wasn't planning to make enemies of the entire world; his plan was simply to deal with one or two major powers, create chaos in Falling Sky Island, and meanwhile make some living space for the part of the Nine States' Cultivators who were moving.
As for how to expand afterward, that would be the work of The Nine States itself—Fang Xi had no intention of helping them slaughter all the Alien race Integrated Cultivators on Falling Sky Island.
If they couldn't even manage this, then there was no need to talk about going to the Earth Immortal Realm to avenge the Fang Immortal Taoist Master.
Moreover,
Immortal Cultivators' various unique Secret Skills and Secret Arts were endless, when specifically targeted, even Immortals would surely come to a bad end!